Microelectronic devices utilize semiconductor integrated circuits which incorporate numerous electronic components. These circuits consist of numerous circuit elements, such as, transistors and resistors, electrically connected to perform various functionality. Typically, the circuit is mounted on a substrate which physically supports the integrated circuit and helps to electrically interconnect elements of the circuit. The substrate may be part of a discrete chip package used to hold a single chip or integrated circuit.
The chip may be mounted on a printed circuit board (PCB) or other platform used for interconnecting one or more chips together and to other electronic components. Connections may be made through conductive pathways, wire bonding or wrapping, etc. The design and layout of the components on a PCB are important to increase functionality associated with the components. The higher the number of electronic components that are interconnected, the greater the functionality associated with those components. However, there is only so much real estate on a PCB.
To achieve additional functionality without significantly increasing the size of the PCB, one or more chips containing integrated circuits may be mounted on top of each other within a single semiconductor package. This stacking of chips increases the amount of circuitry available on a PCB, and further simplifies the board assembly process. For example, four or more chips may be stacked together to provide varying functionality, such as, memory, logic, analog, mixed signal technologies. As a result, board design is able to take advantage of horizontal and vertical integration of chips.
However, chip operation inherently generates heat. The electrical power dissipated throughout a chip tends to heat the chip and its corresponding substrate. As the device is turned on, operates, and then turns off, numerous heating and cooling cycles affect the chip. That is, the temperature of the chip and substrate will rise and fall throughout the life of the integrated circuit. This leads to thermal expansion and contraction of the chip and substrate. As a result, components may become damaged, become dislodged, and become disconnected from other elements.
As more and more chips are stacked within a package, heat dissipation becomes an even more critical issue. Thus, a package should be capable of dissipating the heat generated by the operation of the enclosed chips, so as to limit the temperature rise of chips within the semiconductor chip package.